1. Field of the Invention
The present invention relates to a process for curing a thermal epoxy that couples an integrated circuit to a thermal element.
2. Background Information
Integrated circuits can be assembled into packages that are soldered to a printed circuit board. The integrated circuit is typically mounted to a substrate and enclosed by an encapsulant. Integrated circuits generate heat that must be removed from the package. Some integrated circuit packages incorporate thermal elements such as heat spreader to improve the thermal performance of the package. The heat spreader may be coupled to a surface of the integrated circuit by a thermal grease or a thermal epoxy.
The thermal epoxy may be cured in an oven that heats the entire package. The coefficient of thermal expansion of the substrate is typically different than the expansion coefficient of the integrated circuit and the thermal element. When the thermal epoxy is heated in the oven the different coefficient of expansions may create a warpage in the package. The warpage may induce a pumping action of the thermal epoxy so that epoxy flows out of the integrated circuit/thermal element interface. This pumping event may create an air gap between the integrated circuit and the thermal element. Air has a low coefficient of thermal conductivity. The existence of air increases the thermal impedance of the package and the junction temperatures of the integrated circuit. It would be desirable to provide a process that cures the thermal epoxy without heating the other elements of the package.